Physiology of Wound Healing

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Questions and Answers

What best differentiates regeneration from repair by fibrosis?

Regeneration leads to scar formation, while repair by fibrosis does not.

Regeneration fully restores structure and function, while fibrosis repairs but does not restore function. (correct)

Regeneration requires fewer immune responses than repair by fibrosis.

Regeneration occurs only in labile cells, whereas repair by fibrosis occurs in stable cells only.

Which of the following cell types is accurately defined in relation to tissue turnover after injury?

Labile cells have slow regeneration capabilities.

Permanent cells can regenerate tissue indefinitely.

Stable cells are incapable of division and repair.

Labile cells can rapidly divide and replace lost tissue. (correct)

Which stage of the cell cycle is most directly involved in regulating cell division and could lead to pathology if disrupted?

S phase, where DNA synthesis occurs.

M phase, where mitosis happens. (correct)

G1 phase, responsible for cell growth.

G2 phase, prior to cell division.

Which of the following healing intentions is characterized by delayed closure and can often lead to scarring?

Secondary intention, which involves extensive tissue loss. Signup and view all the answers

Which statement accurately describes labile tissues?

They can continuously divide and regenerate if stem cells are available. Signup and view all the answers

What is the most significant factor that can influence the outcome of wound healing?

Oxygen levels in the healing tissue. Signup and view all the answers

What is the primary role of growth factors in tissue repair?

They trigger cell differentiation and promote cell division. Signup and view all the answers

Which of the following best explains the behavior of stable tissues during injury?

They have limited regenerative capacity but can respond to stimuli by re-entering the cell cycle. Signup and view all the answers

Which type of tissue is characterized as terminally differentiated and does not proliferate?

Permanent tissues that primarily heal through scar formation. Signup and view all the answers

Which statement about the proliferation phase of wound healing is correct?

This phase is characterized by the predominance of fibroblasts and formation of granulation tissue. Signup and view all the answers

What role do cytokines and growth factors play in fibroplasia?

They stimulate the replication and proliferation of fibroblasts. Signup and view all the answers

Which type of collagen is predominantly formed during the maturation phase of wound healing?

Type I collagen Signup and view all the answers

What is the primary function of the extracellular matrix (ECM)?

To provide a scaffold for tissue renewal. Signup and view all the answers

Which statement about wound closure classifications is correct?

Secondary intention involves leaving superficial layers open to granulate. Signup and view all the answers

What is the major characteristic of the ECM's interstitial matrix?

It provides structural support between cells. Signup and view all the answers

Study Notes

Wound Healing Overview

Wound healing involves injury response aiming to restore anatomical structure and function.
Two processes: regeneration (cellular replacement) and repair (fibrosis).
Healing outcomes depend on the tissue type and existing conditions.

Regeneration vs. Repair

Regeneration: Replacement with identical cells, allowing complete restoration.
- Limited in mammals; notable in specific cells (e.g., hepatic cells, epithelial stem cells).
Repair: Formation of scar tissue when identical cells are unavailable due to infections or injury.

Cell Types and Turnover

Labile Cells: Constantly divide (e.g., hematopoietic cells, gut epithelium), enabling ready regeneration.
Stable Cells: Quiescent but can proliferate (e.g., liver, kidney); limited regeneration potential.
Permanent Cells: Terminally differentiated, non-proliferative (e.g., neurons, cardiac muscle), leading to scar formation instead of regeneration.

Cell Cycle and Disease

Controlled by the cell cycle, disruption can lead to increased pathological conditions like cancer.
Non-dividing cells may exit the cycle into G0 phase; proliferation mainly occurs in G1 and M phases.

Key Processes in Wound Healing

Stages of Wound Healing

Hemostasis: Initial response to prevent blood loss.
Inflammation: Immune response to clean the wound, lasting several days.
Proliferation: Occurs 3-21 days post-injury, characterized by the formation of granulation tissue and epithelial regeneration.
- Re-epithelialization: Migration of keratinocytes to form a protective barrier.
- Granulation Tissue: Composed of fibroblasts, new blood vessels, and immune cells; essential for healing.
- Angiogenesis: Growth of new blood vessels, supplying oxygen and nutrients.
- Fibroplasia: Fibroblasts proliferate, laying down collagen and extracellular matrix (ECM).

Growth Factors and Cytokines

Secreted by immune cells, crucial for tissue repair and influencing cell division, migration, and differentiation.
Examples include PDGF (cell chemotaxis), TGF-beta (fibroblast migration), and EGF (keratinocyte proliferation).

Extracellular Matrix (ECM)

Provides a scaffold, mechanical support, and stores growth factors for tissue renewal.
Two forms: interstitial (between cells) and basement membrane (between epithelium and mesenchyme).

Collagen in Healing

Type I Collagen: Most abundant in adult tissues, predominant in healed wounds.
Type III Collagen: Common during early healing stages, replaced by Type I during remodeling.

Maturation and Remodeling

Involves wound contraction via myofibroblasts and collagen remodeling over weeks to years.
Type III collagen replaced by Type I, increasing tensile strength to near normal levels.

Healing Intentions

Primary Intention: Wound edges approximated, minimal scarring.
Secondary Intention: Superficial layers left open to granulate; longer healing, wide scarring.
Tertiary Intention: Delayed closure; deep layers closed, superficial layers monitored.

Factors Influencing Healing

Systemic Factors: Infection, malnutrition, ischemia, vitamin/mineral deficiencies, age, smoking, diabetes.
Complications:
- Deficient scar formation: Dehiscence, ulceration.
- Excessive scar formation: Keloids, hypertrophic scars.
- Exaggerated contraction: May deform surrounding tissues, compromising joint motion.

Important Cell Types

Fibroblasts: Central in granulation tissue migration and matrix formation.
Macrophages: Involved in inflammatory response and cytokine production for healing.

Key Mediators

Growth factors (e.g. PDGF, TGF-alpha) stimulate cell proliferation, migration, and collagen synthesis.
Cytokines (e.g. interleukins) regulate immune responses and tissue healing processes.

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Description

This quiz covers the essential concepts of wound healing physiology, including the differentiation between regeneration and fibrosis. It explores the stages of the cell cycle and the implications of disruptions, as well as the roles of labile, stable, and permanent cells in tissue repair. Understand the multifaceted process of healing and scarring.

Physiology of Wound Healing - Fall 2024